# Arduino Nano controlling led strip - cant power leds

I bought a arduino nano (ATmega328P Nano V3) and a led strip (sk6812 3535 4mm), to control the led strip with the arduino. Now i ran into problems with the power supply i guess.

The idea came from this video. First i soldered it like he showed at 4:03. But i messured the power at the VIN Pin and it was just ~4.2 V. Then i messured the 5V pin, which had like 4.8 V, so i resoldered the wires.

Right now it looks like this: I used the 5V charger from my mobile phone to power the Arduino. I cut down the 60 leds to 4, for testing

So i guess i need to connect an external powersupply, like shown here, but to use 5V instead of 12:

I uploaded this code to the arduino:

#include <Adafruit_NeoPixel.h>

#define PIN 4
#define NUMPIXELS 4

void setup() {
pixels.begin();
pixels.setPixelColor(3, pixels.Color(0, 150, 0));

pixels.show();
}

void loop() {

}


Now my questions:

1) Why does my current wireing not work with 4 Leds?

2) Do i need an additional power supply?

3) If i wire it like in the second picture, what can i use as power supply? Can i use any usb-cable, cut it and use it with a normal phone charger? Do i still need to power my arduino with usb b?

• "V" is not the unit of power. – Long Pham Oct 28 '18 at 16:02